Can I switch from a retirement extension to a marriage visa without keeping my bank account in Thailand?

Change banks

Was curious how easy/difficult it would be to do the same thing. For someone to go from a. Extension based on retirement to marriage without leaving the country.

If you used banked money method as your proof of funds for the extension you're currently on now you do indeed need to continue to meet the seasoning requirement

That means you kept 800K baht in the account for 3 months after the extension was granted last year and then don't let the balance go below 400K baht the whole rest of the year until you apply for a new yearly extension.

I would say as long as you didn't have any "down time" between switching the accounts (as in all the money was moved electronically from one account to another instantly) you'd be okay. Pulling it out in cash and redepositing it in another account would not work. 😕

You have to show that year transaction report that you kept a balance of 400K baht when you go to get the new extension based on marriage because you were on one based on retirement using banked money.